The invention relates generally to medical devices, and more particularly to an improved connector assembly for connecting an ultrasound transmission member to an ultrasound transducer for use in an ultrasonic angioplasty catheter.
In typical percutaneous transluminal coronary angioplasty (xe2x80x9cPTCAxe2x80x9d) procedures, a guiding catheter having a preformed distal tip is percutaneously introduced into the cardiovascular system of a patient through the brachial or femoral arteries and advanced therein until the distal tip is in the ostium of the desired coronary artery. A guide wire and a dilatation catheter having a balloon on the distal end are introduced through the guiding catheter with the guide wire slidably disposed within an inner lumen of the dilatation catheter. The guide wire is first advanced into the patient""s coronary vasculature until its distal end crosses the lesion to be dilated and then the dilatation catheter is advanced over the previously introduced guide wire until the dilatation balloon is properly positioned across the lesion. The balloon may then be inflated to treat the lesion. Thereafter, a stent device may be located at the treated lesion, if deemed necessary.
In xe2x80x9cultrasonicxe2x80x9d angioplasty, an ultrasonic angioplasty catheter is similarly advanced to an area of vascular blockage, and mechanical vibration at ultrasonic frequencies, generated typically by a piezoceramic transducer, is delivered along an elongated ultrasonic angioplasty transmission member or wire to a distal catheter tip. When the distal catheter tip is abutted against intravascular blockage, the vibration of the distal end of the ultrasonic angioplasty transmission member removes the obstruction by mechanical impact and cavitation.
Ultrasonic angioplasty transmission members are commonly connected to an extra-corporeal source of ultrasonic energy, so that it is generally necessary to deliver the ultrasonic energy over a relatively long distance, such as approximately 150 cm., to the intravascular blockage to be treated. Over such a distance, the ultrasonic energy attenuates as it passes along the length of the ultrasonic angioplasty transmission member, resulting in a loss of system efficiency, and requiring the delivery of a greater amount of acoustic energy to the ultrasonic angioplasty transmission member than actually reaches the treatment site, which can increase fatigue of the ultrasonic angioplasty transmission member and thereby increase the chances of fracturing and breakage during use, especially when the wires are bent. It is therefore desirable to provide an ultrasonic angioplasty transmission member mounting that has a lower loss of the ultrasonic energy so that lower levels of energy may be applied to the member.
Amplification of the ultrasonic vibrations typically occurs at areas of reduced cross-sectional diameter. Regions where the highest amplification occurs are generally located where the transition to a reduced diameter occurs, at the proximal end of a smaller diameter section where transverse vibration of ultrasonic energy transmitted from a larger section is amplified. These areas are prone to higher stresses due to increased longitudinal and transverse vibration as a result of amplification. One such area is a connection point of the ultrasound transmission member to the ultrasonic transducer. There typically exists a significant step down resulting in amplification. Firmly connecting the member to the transducer will result in fewer inefficiencies.
Accurate positioning of the ultrasonic angioplasty catheter and ultrasound transmission member in the vascular system to be treated is important for the successful application of ultrasonic energy to an intravascular blockage. It is therefore desirable that the ultrasound transmission wire and ultrasound transducer be firmly aligned with the catheter. It is important that as few losses as possible occur between the application of ultrasonic energy to the ultrasonic wire at its proximal end by the ultrasound transducer and the application of that ultrasonic energy at its distal end to the vascular blockage. The ultrasonic angioplasty transmission member should not rotate independently of the rest of the catheter due to transverse or longitudinal vibrations. Rotation of the wire inside the catheter dampens the transmission of ultrasonic energy through the wire resulting in a less efficient energy transfer. Firmly mounting the wire in place will increase the efficiency in that less energy is absorbed by the wire.
Since the connection point of an ultrasonic transducer to the ultrasound transmission wire is the region where the greatest amplification of ultrasonic energy occurs due to the large reduction in diameter, it is possible for the ultrasonic angioplasty transmission member to rotate independently of the rest of the catheter due to transverse or longitudinal vibrations during use. Such rotation can interfere with the accurate positioning of an ultrasonic angioplasty catheter and the included ultrasound transmission member in the vascular system. While conventional connector assemblies are known that firmly grip and hold the ultrasound transmission member in relation to the ultrasound transducer, they can permit rotation of the ultrasound transmission member and connector assembly relative to the ultrasonic angioplasty catheter during use.
An ultrasound catheter having an ultrasound transmission member or wire and a proximal end member connector assembly is known from U.S. Pat. No. 5,382,228 to Nita et al. The proximal end member connector assembly of U.S. Pat. No. 5,382,228 can include a compressible gripping ferrule, compressible plugs, or a combination of both, for securing the ultrasound transmission member or wire to an ultrasound transducer. The compressible gripping ferrule is received in a proximal connector member threadedly connected to a transducer horn, and has a small aperture through which the ultrasound transmission member passes. A frontal member compresses the gripping ferrule to cause the gripping ferrule to firmly grip and hold the ultrasound transmission member to the transducer. The proximal connector member can then be compressed or crimped inwardly to additionally hold the ultrasound transmission member. Although the ""228 patent represents an advance in the art, such a connector assembly can permit rotation of the ultrasound transmission member and connector assembly relative to the ultrasonic angioplasty catheter, particularly under the stress of longitudinal and transverse vibrations during use.
Hence, those skilled in the art have recognized a need for an improved connector assembly to more efficiently transfer ultrasonic energy to an ultrasound transmission member to lessen inefficiencies. Further, those skilled in the art have recognized a need for a mounting system that keeps the connector assembly and the ultrasound transmission member from rotating independently relative to the ultrasonic angioplasty catheter. The present invention fulfills this need and others.
Briefly, and in general terms, the present invention is directed to an improved connector assembly for connecting an ultrasound transducer and an ultrasound transmission member of an ultrasonic angioplasty catheter. Further it is directed to an improved device to prevent the connector assembly and ultrasound transmission member from rotating independently relative to the ultrasonic angioplasty catheter.
In one aspect, there is provided an ultrasonic angioplasty device for connection to an ultrasound transducer, the ultrasonic angioplasty device comprising an elongated catheter body having a lumen extending longitudinally therethrough, the catheter body having a proximal end and a distal end, an ultrasound transmission member located in the lumen of the catheter body and having a distal end for applying ultrasonic energy to a biological subject, and having a proximal end, a connector assembly configured to connect the proximal end of the ultrasound transmission member to an ultrasound transducer, and a rotation control device comprising a control shaft disposed at the proximal end of the ultrasound transmission member and coupled to the proximal end of the elongated catheter body such that rotation of the control shaft controls rotation of the catheter body, and comprising an interconnection device interconnecting the connector assembly with the control shaft that prevents rotation of the connector assembly and the ultrasound transmission member relative to the control shaft thereby preventing rotation of the ultrasound transmission member relative to the catheter body.
In more detailed aspects, the interconnection device of the rotation control device comprises a fastener for aligning and interconnecting the connector assembly with the control shaft. The connector assembly in another aspect comprises a key member and the control shaft comprises a surface defining a correspondingly shaped slot for receiving the key member for preventing rotation of the connector assembly relative to the control shaft. In yet more detail, the connector assembly comprises a compressible gripping ferrule having a surface defining an aperture through which the ultrasound transmission member passes, a front connector screw member having a surface defining an aperture through which the ultrasound transmission member passes and having an exterior threaded portion, and a crimp screw connector member connectable to the ultrasound transducer, the crimp screw connector member having a surface defining an aperture through which the ultrasound transmission member passes and having a longitudinal bore in which the compressible gripping ferrule is disposed, the longitudinal bore having an internally threaded portion for threadably receiving the exterior threaded portion of the front connector screw member, whereby the front connector screw member compresses the gripping ferrule in the crimp screw connector member, to cause the gripping ferrule to firmly grip and hold the ultrasound transmission member
In further aspects, the control shaft includes a surface defining a first transverse bore, the crimp screw connector member has a surface defining a second transverse bore, and the rotation control device comprises a dowel member disposed in the first and second transverse bores to align the control shaft and the crimp screw connector member to prevent the crimp screw connector member and the ultrasound transmission member from rotating relative to the control shaft and thereby preventing the ultrasound transmission member from rotating relative to the elongated catheter body. In another detailed aspect, a key member is disposed on the crimp screw connector member, and wherein the control shaft has a surface defining a correspondingly shaped slot for receiving the key member for preventing rotation of the crimp screw connector member relative to the control shaft.
In yet other aspects, the key member comprises an annular member having a square outer shape. In another aspect, the key member captures the crimp screw connector member, and wherein the key member has a surface defining an aperture for receiving a portion of the crimp screw connector member, and the portion of the crimp screw connector member and the aperture of the key member have corresponding shapes for preventing rotation of the crimp screw connector member relative to the key member. Further, the aperture of the key member has a square shape.
These and other aspects and advantages of the invention will become apparent from the following detailed description and the accompanying drawings, which illustrate by way of example the features of the invention.